UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 1 of 17 

## (U) Fire Extinguishing Agents for Protection of Occupied Spaces in Military Ground Vehicles

Steven E. Hodges, Ph.D. Senior Scientist, Principal Alion Science and Technology Santa Barbara, CA 93105 steven.e.hodges1@us.army.mil Steven J. McCormick Team Leader, Damage Reduction Army TARDEC Ground Systems Survivability

Warren, MI 48397 steven.j.mccormick @us.army.mil

(U) ABSTRACT

(U) Historically the US Army (USA) used Halon 1301 (bromotrifluoromethane), a chemical with high Ozone De pletion Potential (ODP), to protect the crews of armored vehicles from the effects of peacetime and combat fires. Since the phase

- out of Halon production the USA has directed that zero ODP materials be used wherever possible. Subsequently

, major new vehi cle platforms have been deployed with Automatic Fire Extinguishing Systems (AFES) that rely on HFC

- 227 BC, a zero

- ODP

- agent blend of HFC

- 227ea (heptafluoropropane) and sodium

- bicarbonate

- based dry chemical. Unfortunately , hydrofluor o carbons (HFCs) general ly have high Global Warming Potential (GWP)

- thousands of times that of carbon dioxide on a weight basis. Hence, as part of a larger effort to reduce its carbon footprint, USA Program Managers have asked that more environmentally friendly fire extinguish ing agents be evaluated as part of ongoing vehicle modernization efforts. Several agents are being investigated

, including FK

- 5

- 1

- 12, water with additives, and dry chemicals. This report describes the findings of more than 150 live

- fire tests using nine agents and four extinguisher technologies. The basic conclusion is that no alternate agent can yet be considered to be a drop

- in replacement for Halon 1301 or HFC

- 227BC for this application. However, a blend of Halon 1301 and dry chemical has been found to be about twice as effective as Halon 1301 alone. Thus, pending confirmation tests on vehicles, it may be feasible to use less Halon in legacy systems without compromising fire protection performance.

DISTRIBUTION A : Approved for Public Release; Dist ribution is Unlimited.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 2 of 17 (U) INTRODUCTION

(U) By 1982 the first modern

, automatic fire extinguishing system (AFES) designed to protect the crew from combat

- induced fires was deployed on a US Army (USA) vehicle , the M1 Abrams main battle tank

. AFES are com prised of four major components : fast fire sensors, control electronics, fast

- opening fire extinguisher s , and integration wiring and bracketry (ref. 1

, 2 )

. Subsequently

, the USA fielded similar systems on other platforms including the Bradley Fighting Ve hicle ( BFV ) and Field Artillery Ammunition Supp ort Vehicle ( FAASV )

.
(U) In Army tests

, AFES were able to detect and suppress combat fires ( i.e., fast

- growth fuel oil deflagrations ) in a fraction of a second (ref. 1, 2 ). In Desert Storm b attle d amage

a s sessments , the system s were reported to have been effective (ref. 3). These systems all used extinguishers filled w ith Halon 1301 (bromotrifluoro methane)

.
(U) In compliance with the requirements of the US Clean Air Act Amendments of 1990 and in conform ity with the Montreal Protocol (MP) of 1987, Halon 1301was phased out of production at the end of 1993. Subsequently

, the USA decided to use substances with zero ozone depletion potential ( OD P) wherever possible. Since then

, AFES have been deployed on ST RYKER, Up

- Armored High Mobility Multipurpose Wheeled Vehicles (Up

- Armored HMMWV or UAH)

, Mine Resistant Ambush Protected (MRAP) vehicles and other platforms

, including the US Marine Corps‟ (USMC) Light Armored Vehicle (LAV) and Expeditionary Fighting Vehic le (EFV)

. These AFES use similar detection and controls as used in older systems but rely on extinguishers filled with a more environmentally friendly agent: HFC

- 227BC (also known as FM

- 200BC) , a blend of HFC

- 227ea (heptafluoropropane) and sodium

- bicarbon ate

based dry chemical. HFC

- 227ea , an HFC, has zero ODP so i t s continued production is acceptable under t he MP. The blend was developed by the Army as part of an effort to find Halon

- alternate fire extinguishing agents, and was demonstrated to be essenti ally as effective as Halon 1301 and adequat e as a Halon replacement (ref. 4 ). The STRYKER Brigade Combat Team (BCT) was the first USA vehicle to be qualified with HFC

- 227BC as its crew agent (refs. 5, 6 ). New vehicles, including Joint Light Tactical Vehi cle (JLTV) and MRAP All

- Terrain Vehicle (MATV)

, currently specify HFC

- 227BC for the crew AFES. Table 1 lists (in order of qualification ) the agent used in the crew AFES of major USA and USMC platforms. The Army relies on its Halon reserve to support legac y vehicles.

(U) However, HFC materials such as HFC

- 227ea have high Global Warming Potential (GWP)

- thousands of times that of carbon dioxide. Hence
, as part of a larger effort to reduce its carbon footprint, the USA has begun looking at more environme ntally friendly fire extinguishing agents. Several agents are being evaluated

, including FK

- 5

- 1

- 12 , water with additives, and dry chemicals. This report describes the findings of that project based on more than 150 live

- fire tests using nine agents and f our extinguisher technologies. It should be noted that c onverting an existing system from one agent to another involves many steps, achieving acceptable fire suppression performance discussed in this paper being a key one. Other steps are listed in ref. 7

.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 3 of 17 Table 1 . (U) Crew AFES agents in order of qualification.
Platform Crew AFES Agent

Abrams Main Battle Tank Halon 1301 Bradley Fighting Vehicle (BFV) Halon 1301

* Field Artillery Ammunition Supp ort Vehicle ( FAASV ) Halon 1301 USMC Expeditionary Fightin g Vehicle (EFV) HFC

- 227BC

STRYKER Brigade Combat Team (BCT) HFC

- 227BC

U p

- Armored H MMWV (UAH) HFC

- 227BC

M ine R esistant A mbush P rotected (MRAP) HFC

- 227BC USMC Light Armored Vehicle (LAV) HFC

- 227BC

MRAP A ll

- Terrain V ehicle (MATV) HFC

- 227BC

* * J oint L ight T actical V ehicle (JLTV) HFC

- 227BC

* ** F uture C ombat S ystems (FCS) HFC

- 227BC *Upgrade to HFC

- 227BC in process * * In development *** Manned Ground Vehicle Cancelled

Table 2

. (U) Agent P roperties

. Property Halon

1301 HFC

227ea a FK

- 5

- 1

- 12 b Water + c Dry Chemical d Environmental Ozone Depletion Potential e 16 0 0 0 0
Global Warming Potential f 6900 3500 1 0 0
Atmospheric Lifetime (yr) 65 33 0.014 0 0 Safety Design Concentration (% v/v ) 5 8.7 6.7 g ~300 g/m 3 ~300 g/m 3

NOAEL

h (%) 5 9.0 10 NA TBD j

LOAEL i (%) 7.5 >10.5 10 NA TBD j Physical Boiling Point (°C)

- 58

- 16 49 115 N/A Vapor Pressure @ 21°C (bar) 13.7 4.1 0.41 0.03 N/A Liquid Density (g/cm 3 ) 1.56 1.39 1.60 1.27 2.16 Molecular Weight (g/mol) 149 170 316 31 84 Heat of Vaporization (J/g ) 117 132 88 >2250 N/A
a) HFC

- 227ea is a form of heptafluor o propane and is sold as a fire extinguishing agent. b) FK

- 5

- 1

- 12 is a perfluorinated six

- carbon ketone manufactured and sold as a fire extinguishing agent. c) Water with 50% Potassium Acetate. d ) Values given are for s odium b icarbonate

- based dry chemical. Potassium b icarbonate crystal density is 2.17 g/cm 3

. e) CFC11 baseline, ref. 8 . f ) CO 2 baseline, ref. 9 . g) Concentration advised by the agent manufacturer representative for this application

. h) No Observed Adverse Effects Level. i ) Lowest Observed Adverse Effects Level. j) A cceptable concentration levels for this application to be determined by the USA

.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 4 of 17 (U) Table 2 lists key properties for the basic agents used in the tests described in this paper. The agents that are mi xtures of a fluorocarbon agent ( i.e., Halon 1301 ; HFC

- 227ea; or FK

- 5

- 1

- 12)

, and dry chemical have essentially the same environmental and safety properties as the base fluorocarbon agent. The environmental properties illustrat e part of the motivation for this study: Halon and HFC

- 227 BC , the agents currently used in A rmy crew systems, have high GWP, and Halon has a relatively high ODP so its production is prohibited by the MP and its use is limited by Army polic y. FK

- 5

- 1

- 12 has zero ODP but a finite GWP

– equivalent to carbon dioxide ( CO 2 ). A r ecent EPA finding has listed several Green House Gases (GHGs)

, including CO 2 , as a threat to public health (ref. 10 ) and recent legislation has proposed significant redu ctions in GHG prod uction (ref. 11 ). Although future limitations on the use of n ear

- zero GWP materials such as FK

- 5

- 1

- 12 are not anticipated, if limitations are imposed, they should be mitigated by the fact that relatively little FK

- 5

- 1

- 12 and similar fire suppression chemi cals are emitted compared to CO 2
.

(U) APPROACH

(U) The Tank and Automotive Research, Development and Engineering Center‟s (TARDEC)
purpose for the tests described here in was to compare the performance of deployed suppres sion agents and more environmenta lly friendly ones. Distinguishing the performance of the agents was facilitated by operating close to where the extinguisher system is overmatched by the fire; the ideal was to bracket the fire with successful and failed suppression in a repeatable way fo r each agent tested. We therefore invited t hree extinguisher suppliers to support the tests

– and asked them to provide suppression systems based on various agents and concentrations that would yield marginal suppression „passes‟ and „failures‟ based on c urrent vehicle performance criteria. Note that the amount of agent used was often less than the design concentration used in production systems.

(U) The tests were conducted at the Army‟s Aberdeen Test Center (ATC) in a 260 ft 3 (7.36

m 3 ) box with relative ly little clutter

, no active air flow , and hatches closed (Figure 1)

. Although
t he exploratory test box volume is similar to some legacy v ehicle crew compartment volumes, it does not represent a specific application. Tests were conducted at the outdoor a mbient temperature at the test site which ranged from approximately 25 to 90°F (

- 4 to 32°C )

.
(U) Figure 2 shows the test box with sampling points, fire position and flame path, extinguisher positions and agent discharge direction s indicated.

(U) The te st box was instrumented to measure blast overpressures, temperatures and the chemistry of the atmosphere

, in particular the combustion byproducts. The response times of the thermocouples were too long to effectively measure the brief excursions that could have caused skin

- burn injury

– however they ga ve a gross indi cation of the air temperature. For this reason and b ecause t he thermal excursions measured were benign

, those results are not reported. A high

- speed video camera recorded the fire and its suppr ession from the top of the box.

(U) The fires were detected by a production infrared optical fire sensor that, via a simple controller, released the extinguishers. The average time to valve activation was approximately 40 ± 5 ms after the first pressure and/or infrared signature was observed in the ballistic data.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 5 of 17 (U) The Field Chemistry Sampling and Analysis Team at ATC measured the combustion byproducts during the tests , including carbonyl fluoride (COF 2 ) and hydrofluoric (HF) acid . The atmosphere w as sampled from four positions within the test box (Figure 2). A technique specifically developed by the ATC Field Chemistry group to distinguish FK

- 5

- 1

- 12 and COF 2 (ref. 12) was employed. ATC subsequently reported the chemistry results (ref. 13) includi ng casualty assessments for each test based on current vehicle performance criteria (ref. 14).

Figure 1. (U) Exploratory Test Box a) Exterior and b) Interior

.

Figure 2. (U) Extinguisher Positions, Blast Overp ressure and Chemistry Sample Po i n t s in the Test Box.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 6 of 17 (U) The „Pass/Fail‟ criteria used are based on the current USA crew casualty criteria applied to armored ground vehicles

. Table 3 lists major excerpts and derivations from the formal requirements (ref. 14)

. It is important to note that current criteria are under review and may be revised (ref. 15).

Table 3

. (U) Selected Crew AFES Performance Criteria.
Parameter Requirement a Test b
Fire Suppression Extinguish all flames without reflash Y

Skin Burns Less than second degree burns (<2400°F

- sec over 10 seconds or heat flux < 3.9 cal/cm 2 ) c

Overpressure Less than 11.6 psi Y Agent Concentration Not to exceed LOAEL d Y

Acid Gases (HF + HBr + 2∙COF 2 ) Less than 746 ppm

- min (5 min dose ) Y

Oxygen Levels Not below 16% e Y Discharge Impulse Noise No hearing protection limit: < 140 dBP f Single hearing protect ion limit : < 1 65 dBP f N

Discharge Forces Not to exceed 8 g g and <20 psi at 5 inches h N
( a) Based on reference 14 a except as noted

. ( b) Addressed in Exploratory Tests. ( c) Temperature recorded with thermocouples. ( d) Lowest Observed Adverse Effects Level per ref 16

. (e) ref. 14b. (f) ref. 14c. (g) Extrapolated from ref. 14a. (h ) ref. 15.

(U) In industrial explosion protection tests, the volume

- normalized speed of an explosion is often calibrated using a parameter called K max , defined as (ref. 17 )

(1)

where P is the blast over pressure, t is the ti me and V is the test box volume. The results for five baseline fire tests with no suppression yielded an average K max of 2.7 bar

- meter/seconds with a standard deviation of 0.2. Due to significant fluctuations in the pressure traces after the agent and fi re interact , and to better facilitate the „real

- time‟ nature of these exploratory tests, a variant of K max given in equation (1) was used :

(2)

(U) In equation (2), ∆ P is the pressure change during a time interval ∆ t

. In these tests, K was determined using a predetermined interval starting at the time the extinguishers were activated

. The target for the fires was a K value of 1 to 2 bar

- meter/seconds

.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 7 of 17 (U) AGENTS AND EXTINGUISHERS

(U) Nine suppression agents were used (the short

- hand names in parenthesis are used in subsequent charts and tables) :

• Halon 1301 ( „H alon ‟ )

• Halon 1301 with Sodium Bicarbonate

- based Dry Chemical („ Halon+ ‟ )

• Halon 1301 with Potassium Bicar bonate

- based Dry Chemical („ HalonK ‟)

• HFC

- 227ea with Sodium Bicarbonate

- based Dry Chemical ( „ HFC 227BC ‟)

• FK

- 5

- 1

- 12 ( „ FK

- 5

- 1

- 12 ‟ )

• FK

- 5

- 1

- 12 with Sodium Bicarbonate

- based Dry Chemical ( „ FK

- 5

- 1

- 12+ ‟ )

• Water with Potassium Acetate

- based additives ( „ Water+ ‟ )

• Sodi um Bicarbonate

- based Dry Chemical („NaBC ‟)

• Potassium Bicarbonate

- based Dry Chemical („KBC ‟)

(U) As indicated in Table 1 , Halon 1301 is used in the crew compartment of legacy vehicles such as the Abrams and Bradley. „ Halon+ ‟ is a mixture of Halon 1301 and sodium

- bicarbonate

based dry chemical. Although never fielded, this mixture is expected to be compatible with most or all fielded hardware

, in which case current Halon 1301 extinguishers could be recharged with

„ Halon+

. ‟ „ HFC

- 227BC ‟ is also a mixture of a clean agent and sodium

- bicarbonate

- based dry chemical. A specific blend of HFC

- 227BC ( i.e., HFC

- 227ea with 5% by weight dry chemical ) is fielded in the AFES used to pro tect the crew in STRYKER (refs. 5

, 6
, 7 ) , U p

- Armored H MMWV
, MRAP

, upgraded FAASV, and the USMC ‟s Expeditionary Fighting Vehicle ( EFV ) and Light Armored Vehicle (LAV)

. Some MRAP vehicles allow up to 10% by weight dry chemical.

(U) The amount of sodium bicarbonate

- based dry chemical added to the clean agents tested varied from 5% by weigh t , the usual fielded mix, to a much higher fraction. Crew AFES based on HFC

- 227BC use a HFC

- 227ea design concentration of about 9% by volume at 20°C

– a level that ensures the LOAEL is not exceeded at temperature extreme s. In such a system, a 5% by weigh t mix of sodium bicarbonate corresponds to a dry chemical density of 40 g/m 3 in the protected volume. The Army specifies a 5 to 10% by weight mix of dry chemical in HFC

227BC systems. Therefore

, the maximum amount of dry chemical additive used in the tes ts described herein was 80 g/m 3

.
(U) FK

- 5

- 1

- 12 is widely available but has never been fielded in an Army crew

- AFES. Although the „ FK

- 5

- 1

- 12+ ‟ mixture was tested, FK

- 5

- 1

- 12 and sodium

- bicarbonate

- based dry chemical interact chemically and so cannot be sto red together for long periods of time as is done with HFC

- 227ea and dry chemical. However, t he chemical interaction between FK

- 5

- 1

- 12 and the dry chemical did not appear to be significant in the brief period they were stored together for the tests descri bed herein.

(U) A n industrial explosion protection study concluded that, g iven the phase

- out of H alon, sodium

- bicarbonate

- based dry chemical offered “the best compromise between effectiveness and practical acceptance for all but the special cases of occu pied spaces” (ref. 1 8 ). No discussion or reference i s given for why dry chemical is not an acceptable agent for occupied spaces; it may be due to the common

- sense bias against breathing dust. In any case, t he s odium

- bicarbonate

- basedUNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 8 of 17 dry chemical used in th e test series described herein (ref. 19 ) was previously found to be acceptable for use in crew compartments by the USA (ref

. 20 )

. When dry chemical was tested alone, the concentrations used were as high as 300 g/m 3 , higher than the levels seen in field ed HFC

- 227BC systems (40 to 80 g/m 3 based on a 5 to 10% by weight dry chemical to HFC

- 227 ea mix , with the HFC

- 227ea at the maximum safe level ) . Operational issues including clean

- up and obscuration remain to be fully addressed (ref. 21 )

.
(U) This study a lso compared potassium bicarbonate (ref. 22) and sodium bicarbonate, both

as s ole suppression agents and as additive s to Halon 1301. Previous studies have found that for certain types of fires, potassium

- based dry chemical can be as much as twice as effec tive as sodium

- based dry chemical by weight (ref. 23 ). Consequently

, in the tests described herein

, suppression performance was compared with half the potassium

- based agent with respect to the sodium

- based dry chemical.

(U) „ Water+ ‟ is a 50

- 50 mix of wat er and potassium acetate. This mix is available commercially (for example it is used for de

- icing operations at airports) , and was one of two agents TARDEC originally recommended as a Halon 1301 replacement (ref. 4 ). However

, special care must be taken t o prevent reflash fires when integrating a water

- based AFES (ref. 4 ). In addition, operational issues

, such as clean

- up and effects on electrical equipment

, remain to be fully addressed.

(U) A gents were delivered by four e xtinguisher configurations from three independent suppliers :

• N itrogen charged cylinder with a solenoid valve ( used in Abrams, BFV, FAASV, STRYKER, UAH, and some MRAP s ) ; „N 2 Solenoid‟ in Table 4

• Nitrogen charged cylinder with a linear actuated valve ( designed for use in the crew and mis sion bay of FCS ‟ NLOS

- C ) ; „N 2 Linear‟ in Table 4

• N itrogen charged cylinder with a squib actuated valve ( used in some MRAP s ) ; „N 2 S quib ‟ in Table 4

• Gas Generator driven Hybrid Fire Extinguisher ( developmental ) ; „GG HFE‟ in Table 4

(U) DESCRIPTION OF TESTS AND RESULTS

(U) A total of 15 7 live

- fire tests in four series were conducted in the Dec ember 20 08 through September 2009 period

. Each test used two equivalent extinguishers (in positions 1 and 2 indicated in Figure 2) unless otherwise noted.

(U) The ag ents and extinguisher configurations tested are summarized in Table 4

. Table 5 shows the best results obtained for each agent; note that the best performance and minimum agent weights are not obtained simultaneously. The agent weight listed is the least used whil e obtaining a reliable ( e.g., repeated) „pass.‟ Both tables show the number of „ p asses‟ obtained

– agent quantities were adjusted to try to achieve „passes‟ in half the tests

. Table 6 summarizes the failure mechanism(s) ( i.e., limiting criteria ) for each agent tested.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 9 of 17 Table 4

. (U) Exploratory Test Result Summary by Extinguisher, Agent, a nd Hardware.

Agent N 2 Solenoid N 2 Linear N 2 Squib GG HFE Total Tests *Total

‘Passes’ Halon 19 0 0 2 21 12 (57%)
Halon+ 19 0 0 0 19 16 (84%)
HalonK 7 0 0 0 7 4 (57%)
HFC

- 227+ 16 8 1 11 36 17 (47%)
FK

- 5

- 1

- 12 10 0 4 7 21 0
FK

- 5

- 1

- 12+ 6 0 2 7 15 0
Water+ 12 0 1 10 23 12 (52%)
NaBC 13 0 0 0 13 7 (54%)
KBC 2 0 0 0 2 2 (100%)
TOTAL 104 8 8 37 157 70 (45%) *The goal for each agent was to pass half the test s.

Table 5

. (U) Exploratory Test Result Summary Showing Best Results f or Each Agent.

** Performance

Agent Total *Pass **Least

Agent Weight (lb) Lowest Acid Dose (ppm

- min) Lowest

Pressure Peak (psi) Fastest

Fire Out Time (ms) Note
Halon 21 12 ~5 ~500 <1 <200 Legacy fielded product

Halon+ 19 16 ~2.5 <20 <1 <200 New mix compatible with fielded extinguishers

HalonK 7 4 ~2.5 <20 <1 <200 New mix compatible with fielded extinguishers
HFC227BC 36 17 ~5 <20 <1 <200 Fielded product
FK

- 5

- 1

- 12 21 0 >25 ~2,000 1.2 <200 Available

FK

- 5

- 1

- 12+ 15 0 >15 ~1,300 1.6 <200 Invention required

Water+ 23 12 ~4 0 1.5 ~400 Development required; operational issues?

NaBC 13 7 ~3 0 <1 <200 Available; operational issues?

KBC 2 2 ~2 0 <1 <200 Available; operatio nal issues?

Total 157 70 *The goal for each agent was to pass half the tests. **Best Performance and Least Agent Weight are not obtained simultaneously. Acid doses are obtained from ref. 13.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 10 of 17 Table 6

. (U) Summary of L imiting Criteria for Agents T ested

. Agent Limiting Criteria Collateral Criteria Other Issues

Halon Acid Gas Pressure & Temperature Deployed & Stockpiled

Halon+ , K Pressure Acid Gas & Temperature New Agent Mix

HFC227 BC Acid Gas & Reflash Pressure & Temperature Deployed

FK

- 5

- 1

- 12 Ac id Gas Reflash Weight

FK

- 5

- 1

- 12+ Acid Gas Reflash Weight

, Agent Compatibility

Water+ Reflash Pressure & Temperature Clean

- up Dry Chem Reflash Pressure & Temperature Obscuration & Clean

- up

(U) Figure 3 shows the acid

- gas dose measured versus the amoun t of agent released for all of the fluorinated agents for one of the extinguisher configurations. The maximum acceptable acid dose and safe agent weights are also indicated. The minimum measurable acid dose was 20
ppm

- min.

Figure 3

. ( U ) Average Acid Dose I ntegrated over 5

- M inutes versus Agent Density (ref. 13 d

, e )

. The solid line is a „best fit‟ trend using a Power S eries based on the „ HFC

- 227BC ‟ data.

(U) The „ FK

- 5

- 1

- 12 ‟ and „ FK

- 5

- 1

- 12+ ‟ tests with approximately 25 pounds of agent used equivalent e xtinguishers in all three locations shown in Figure 2. The relative trends for „ FK

- 5

- 1

- 12 ,‟ „ FK

- 5

- 1

- 12+ ‟ and „ HFC

- 227BC ‟ indicated in Figure 3 were observed for all extinguishers tested with those agents.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 11 of 17 (U) Interestingly, t he Halon 1301 results shown in Figure 3 indicate little or no advantage to using maximum safe concentrations. The high acid levels measured are consistent with earlier results (ref. 4) and indicate that the test fire is nearly an overmatch of the Halon systems described herein.

(U) Halon+ and HalonK agents were tested wit h one (in position 2) and two (in positions 1 and 2) extinguishers per test , as parenthetically indicated in Figure 3. None of the tests using two extinguishers failed, even when very low Halon concentrations w ere used. Consequently, tests with a single extinguisher were necessary to achieve the desired failures. Note that one of the four „Halon+(1)‟ tests using sodium

- bicarbonate

- based dry chemical „ passed, ‟ while none of the three „HalonK(1)‟ tests, using ap proximately half the amount of potassium

- bicarbonate

- based dry chemical, „ passed. ‟ This suggests that, when mixed with Halon, potassium

- bicarbonate

based dry chemical is not significantly more effective that sodium

- bicarbonate

- based dry chemical

.
(U) Fi gure 4 shows the acid gas dose versus minimum oxygen levels observed for the tests using Halon with potassium

- bicarbonate and sodium

- bicarbonate

- based dry chemical additives. The results indicate that the test fires were limited by the amount of oxygen (v ersus fuel) available and clearly distinguish the „Passes‟ and „Fails

. ‟ Also indicated is that

, in a failed suppression, potassium

- bicarbonate

- based dry chemical with Halon yields somewhat lower acid than Halon with sodium

- bicarbonate

- based dry chemical

.

Figure 4

. (U) Five

- M inute Acid Dose versus Minimum Oxygen L evel for Halon with S odium

and P otassium

- B icarbonate Dry Chemicals (ref. 13e).

(U) Figure 5 compares the integrated blast overpressure versus agent mass density for all agents tested. Altho ugh integrated pressure is not a casualty criteria, because the „passes‟ and „failures‟ based on established casualty criteria are distinguished using this parameter

, it is a convenient method for comparing fluorinated agents that produce acid gas with non flu o rinated agents that do not produce acid gas . T he threshold between a „pass‟ and a „fail‟ appears to beUNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 12 of 17 about 0.2 bar

- s. It is interesting to note that Halon and HFC

- 227BC fail at agent densities of a little less than 0.25 kg/m 3 ; the other agents desc ribed herein (except for the FK

- 5

- 1

- 12

- based agents ) appear to require densities of at least 0.15 kg/m 3

. Because t he FK

- 5

- 1

- 12

- based agents yielded unacceptably high acid levels at the maximum safe concentration (as shown in Fig. 3), they were not tested at low concentrations where a failed suppression resulting in high integrated pressures would have occurred.

(U) Figure 5 includes the results for dry chemical a gents alone , and allows another comparison of sodium

- bicarbonate

- and potassium

- bicarbonate

- b ased dry chemicals : When mixed with Halon, the potassium

- based dry chemical performs about the same as the sodium

based dry chemical , consistent with the results shown in Figures 3 and 4 . However
, when used alone, the potassium

- based dry chemical („KBC‟) is almost twice as effective by weight compared to sodium

- based agent („NaBC‟) , consisten t with earlier findings (ref. 23 )

.
(U) The „W ater+ ‟ tests using proprietary (non

- production) distribution systems performed about as well as other agents on a weight basis as indicated in Figure 5. The successful „Water+‟ tests resulted in fire

- out time s about twice as long as the other agents , as indicated in Table 5

. However, other suppression parameters were comparable to the other agents.

Figure 5

. (U) Integr ated Blast Pressure versus Agent Density for Halon with and without Dry Chemical Additives , HFC

- 227BC, S odium

- and P otassium

- B icarbonate Dry Chemicals and Water with Freeze

- Point Suppressant . The arrows indicate the minimum agent densities required for su ccessful suppression.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 13 of 17 (U) DISCUSSION

(U) A few observations can be made based on the results described above :

Figure 3 indicates that Halon 1301 and HFC

- 227BC performed similarly, although Halon 1301 yielded relatively higher acid doses, consiste nt with earlier findings (ref. 4 )

. Tables 4 and 5 show that FK

- 5

- 1

- 12 was not effective whether used alone or mixed with dry chemical due to high acid gas levels

. Tables 4 and 5 and Figure 5 indicate that dry chemical and w ater with additives may become viable bu t further analysis, development and testing are required. Figure 5 indicates that when used as the sole suppression agent, potassium

- bicarbonate

based dry chemical is almost twice as effective by weight as sodium

- bicarbonate

- based dry chemical, consistent with earlier findings (ref. 2 3 ). Figures 3, 4 and 5 indicate that the mixes of Halon with s odium

- or p otassium

b icarbonate

- based dry chemical s performed similarly. Figure s 3 and 4 indicate that Halon with sodium

- or potassium

- bicarbonate

- based dry chemical s is twice or more as effective by weight as currently deployed crew agents (Halon and HFC

- 227BC ). This result needs to be verified in vehicle

- level tests. No ne of the non

- Halon agents as evaluated are drop

- in replacement s ( i.e., have the same form factor and comparable performance ) for Halon or HFC

- 227BC

.
(U) It should be noted that a mix of Halon 1301 and dry chemical was evaluated previously in one live

- fire test with reasonably good results. In that test

, where a much lower fraction of dry chemical w as used compared to the tests described herein, a s ignificantly reduced acid level was measured compared to the test without the dry chemical (ref. 4 ). This is consistent with the findings reported here in where the amount of Halon 1301 required to success fully extinguish a fire was found to be reduced by a factor of more than two when mix ed with dry chemical. This result needs to be verified with live

- fire tests on application

- representative vehicles.

(U) „Water+‟ consistently knocked the initial fire do wn but reflash was reliably prevented only when proprietary developmental nozzles were used. Dry chemical systems did relatively well when higher

- than

- currently accepted concentrations were applied but were more prone to reflash than all the other agents except „Water+.‟ The higher levels of dry chemical are probably safe for occupied areas but may pose unacceptable operational limitations; for example, a period of obscuration may last many seconds, and clean

- up may be necessary more quickly than the

curr ent minimum acceptable delay of 48 h ou r s

. ( U ) Earlier tests directed at understanding whether FK

- 5

- 1

- 12 i s a viable Halon 1301 replacement in crew AFES w ere conducted by TARDEC (ref. 2 4 ) and the National Research Council of Canada (ref. 2 5 ) using fast

- gr owth fires

. T hese tests yielded similar results: total acid levels were well above current USA incapacitation limits . The tests described here in confirmed those results and extended them by using a wider range of agent concentrations, extinguisher techno logies, and distribution nozzles

. Although a custom nozzle developed for FK

- 5

- 1

- 12 in this application was used (ref. 2 5 ), further improvements in distribution may be possible.

(U) Insight into why FK

- 5

- 1

- 12 performed relatively poorly in these and si milar tests may be obtained by considering that other FK

- 5

- 1

- 12 tests were „ total flooding ‟ and used pan

- fires, notUNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 14 of 17 fast

- growth, explosive fire threats (see ref. 2 6 for example)

. Total f looding systems typically inert a protected volume with sufficient ag ent concentrations to prevent combustion, and the fires are typically small with respect to the protected volume. The tests reported here in matched relatively large, fast

- growing fires with rapid but essentially local agent application , a very different s cenario than typical total flooding

.

Figu re 6

. ( U ) Peak Acid levels for „ HFC

- 227BC ,‟ „ FK

- 5

- 1

- 12+ ‟ and „ FK

- 5

- 1

- 12 ‟ (ref. 13 b )

versus Agent a) Mass and b) Volume Concentration s

. The solid lines in (a) are power curve fits. Note: Although the peak acid levels for „ HFC

- 227BC ‟ and „ FK

- 5

- 1

- 12+ ‟ are similar, the integrated levels used in casualty assessments were very different: none of the FK

- 5

- 1

- 12

- based tests „passed.‟

(U) Fire protection professionals often evaluate suppression agents in terms of the required concentration (usually on a volume percent basis as in ref. 2 6 ). While comparisons based on concentration are valid and useful

, it must be remembered that other agent properties such as required mass must be considered separately. Figure 6 compares peak acid levels measured (ref. 13b) in „ HFC

- 227BC ,‟ „ FK

- 5

- 1

- 12+ ‟ and „ FK

- 5

- 1

- 12 ‟ tests versus mass and volume concentrations (ref. 16 ) . Although the peak acid levels versus concentration for the agents are very similar, especially for the ‟ HFC

- 2 27BC ‟ and FK

- 5

- 1

- 12+ ,‟ the mass of agent that yields a given acid level is very different: far more „ FK

- 5

- 1

- 12+ ‟ than „ HFC

- 227BC ‟ by mass must be delivered to achieve the same acid level.

(U) Note that a lthough the peak acid levels for „ HFC

- 227BC ‟ and „ FK

- 5

- 1

- 12+ ‟ in Figure 6 are similar, the integrated levels used in casualty assessments were very different: none o f the FK

- 5

- 1

- 12

- based tests „passed ,‟ as shown in Figure 3. Th e difference is related to the relative evolution in time of COF 2 and HF . Hal on and HFC

- 227BC tests with good fire suppression show COF 2 quickly peaking and then slowly decaying as the HF level slowly rises ; in FK

- 5

- 1

- 12 tests both COF 2 and HF peak quickly and then slowly decay. The result is that the total integrated acid level u sed in casualty assessments (see Table 3) is higher in FK

- 5

- 1

- 12

- based
tests (ref. 13).UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 15 of 17 (U) As noted earlier, the tests described herein were conducted using a test box without significant clutter and at the ambient temperature at the test site. More co mprehensive, vehicle level tests should address the effects of clutter and operation at temperature extremes (especially low temperatures).

(U) CONCLUSION

(U) Meeting current performance requirements for crew AFES in USA ground vehicles using alternativ es to Halon 1301 and HFC

- 227BC tested to date will require some combination of invention , development and/or increase in space claim and weight compared to fielded systems. The basic result is that, with current products, none of the alternate agents are drop

- in replacements for Halon 1301 or HFC

- 227BC

. However, a blend of Halon 1301 and dry chemical has been found to be about twice as effective as Halon 1301 alone

. Thus, pending confirmation tests on vehicles, it may be feasible to use less Halon in lega cy systems without compromising fire protection performance

.
(U) Disclaimer: Reference herein to any specific commercial company, product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or im ply its endorsement, recommendation, or favoring by the United States Government or the Department of the Army (DoA). The opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or the DoA, and sh all not be used for advertising or product endorsement purposes.

(U) ACKNOWLEDGEMENT S

(U) This program was funded by Ground Systems Survivability ( GSS ) at TARDEC and is a continuation of the work reported previously (ref. 27) . Valuable support and di scussions with Ron Sheinson of the Naval Research Laboratory and Joe Senecal of United Technology Fire & Security are gratefully acknowledged. The excellent support of Aberdeen Test Center‟s Poverty Island R ange 12 team was crucial to completing these tes ts.

(U) REFERENCES

1. (U) A comprehensive description of armored vehicle fire protection approaches through 1995 is given in “ Military Handbook Design of Combat Vehicles f or Fire Survivability ,” MIL

HDBK

- 684. 2. (U) Early AFES components and development are d escribed in Cinzori, R. J., “Dual Spectrum Infrared Fire Sensor,” IRIS, 15 June 1977. 3. (U) Koffinke, MAJ

, “Real Time Battle Damage Assessments,” US Army, Ballistic Research Lab, o n assignment in Desert Storm , 1991

. 4. (U) McCormick, S. J., Clauson, M. and Cros s, H.
, “ US Army Ground Vehicle Crew Compartment Halon Replacement Program ,” Halon Options Technical Working Conference (HOTWC), 2

- 4 May 2000

.UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 16 of 17 5. (U) Hodges

, S. E. and DiRaimo

, L., “ Automatic Fire Extinguishing System (AFES) Alternate Agent Integration Challen ges ,” Proc. 15th Annual Ground Vehicle Survivability Symposium (GVSS), April 2004. 6. Ryzyi, M.

, “Stryker Fire Suppression System Qualification,” Proc. 15th Annual Ground Vehicle Survivability Symposium (GVSS) , April 2004. 7. (U) Hodges, S. E.

, “ Challenges in I ntegrating Halon

- Alternate Agents into Automatic Fire Extinguishing Systems (AFES) ,” Halon Options Technical Working Conference (HOTWC), 2006. 8. (U) World Meteorological Organization (WMO) 1998, Model

- Derived Method 9. (U) Intergovernmental Panel on Climate Ch ange (IPCC) 2001 Method, 100 Year ITH. 10. (U) “Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean A ir Act, Climate Change Division, Office of Atmospheric Programs, US Environmental Protection Agency, 17 April 2009. 11. (U) Waxman and Markey, R eps. , “American Clean Energy and Security Act of 2009 ,” US C ongress, HR2454, 15 May 2009. 12. ( U ) “ FTIR Methodology to Distinguish Novec 1230 and COF 2 Spectra,” ATC Private Communication, March 2009. 13. (U) ATC Chemistry reports: a) 2009

- CC

- 167A, b) 2009

- CC

- 222, c) 2009

- CC

- 227, d) 2009

- CC

- 359 , e) 2009

- CC

- 825

. 14. (U) a) Many current requirements are based on Ripple

, G. and Mundie, T.

, “ Medical Evaluation of Nonfragment Injury Effects in Armored Vehicle Live Fire Tests, ” Walter Reed Army Institute of Research, Sept ember 1989. b) The minimum oxygen level is found in Swanson, G., “ Fire Survivability Parameters for Combat Vehicle Crewmen ,” Memo to the US Army Surgeon General, 20 February 1987. c) Acceptable Noise Levels for this applicatio n are defined in section 6

- 2c(2) of “ Hearing Conservation Program ,” US Army Pamphlet 40

- 501, 10 December 19 9 8

. 15. (U/Limited Distribution) Januszkiewicz, A. J. and Davis

, E. G.

, “ Evaluation of Potential Physical Injury from Mechanical Forces Due to Automatic Fire Extinguisher System Discharge in the STRYKER Combat Vehicle: An Initial Assessment and Recommendations to Prevent Injury ,” Walter Reed Army Institute of Research, 21 August 2003. 16. (U) “NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems 2008 E dition,” National Fire Protection Agency (NFPA), Quincy, MA, 15 August 2007. 17. (U) See for example: Rabash, D. J.

, “Quantification of Explosion Parameters for Combustible Fuel

- Air Mixtures,” Fire Safety Journal, v 11 , ps 113

- 125, 1986. The volume factor is discussed in Eckhoff, R. K.

, “Use of (dP/dt)max from Closed

- Bomb Tests for Predicting Violence of Accidental Dust Explosions in Industrial Plants,” Fire Safety Journal,

v 8 , ps 159

- 168, 1984/85. 18. Moore, P. E., “Suppressants for the C ontrol of I ndustrial E xpl osions,” J. Loss Prev. Process Ind., v 9 (1), ps. 119

- 123, 1996. 19. (U) Dessicarb is described in : “ DXP

- 1

- US/Canada Version,” MSDS KA012, Kidde Aerospace & Defense, 12 Oct ober 2007. 20. (U) “Toxicity Evaluation of Acute Exposure to Dessicarb,” US Army Environme ntal Hygiene Agency, Toxicological Study No. 75

- 51

- Y1F8

- 94, October 1993. 21. (U) Robert G. Daniel, R., and Skaggs, R., “ Test Report: Light Attenuation by Powder Fire Fighting Agents ,” ARL Report for Tests 03

- 14 August 1998, 1998. 22. (U) Potassium

- bicarbonate

- bas ed dry chemical , a lso k nown a s „Purple K‟, is described in http://www.nrl.navy.mil/content.php?P=PURPLEKUNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 17 of 17 23. (U) Reed, M., Fleming, J., Williams, B., Sheinson, R, Chattaway, A., Laverty, N., Spring, D., “Laboratory Evaluation of Bicarbonate Powders as Fire Suppressants,” Proc. International Conference of Ozone Protection Technologies, pp. 333

- 344, 1997. 24. (U) ATC Chemistry Report 2009

- CC

- 016 reports June 2008 test results. 25. (U) See Table 4.1 in Kim, A

. , Crampton

, G. and Kanabus

- Kaminska, M.

, “ Evaluation of Gas Generator System with NOVEC 1230 Agent as a Replacement for Crew Compartment Protection Halon System ,” National Research Council Canada, Report B

- 4193.1 , 31 March 2008. 26. (U) Ditch, B.

, Rivers, P. and Thomas, S.

, “ A Continuation of Thermal Decomposition Product Testing with C 6 F

- K etone, Increased Concentrations ,” Halon Options Technica l Working Conference ( HOTWC ) , May 2002. 27. (U) Hodges

, S. E. and McCormick, S

. J.
, “ Evaluation of Fire Suppression Agents for Protection of Occupied Spaces in Military Ground Vehicles ,” Proc. Ground Vehicle Survivability Symposium (GVSS), August 2009.